Manufacture of mercaptobenzothiazole



Se t. 4, 1951 H. a. H. COOPER EI'AL 2,567,145

MANUFACTURE OF MERCAPTOBENZOTHIAZOLE Filed Aug. 9, 1949 INVENTORS H44l1. COOPF/V CflzPL E. ME/VJ/A/G, d. W

ATTORNEY Patented Sept. 4., 1951 MANUFACTURE OF MERCAPTOBENZO- THIAZOLEHal B. H. Cooper, Bound Brook, and Carl E.

Mensing, Somerville, N. J., assignors to American Cyanamid Company, NewYork, N. Y., a

corporation of Maine Application August 9, 1949, Serial No. 109,362 3Claims. (01. 260306) This invention relates to the production ofmercaptoarylthiazoles, particularly those such as 2- developed on alarge scale, is the production of 2-.mercaptobenzothiazole based on thereaction of a mixture of aniline and sulfur dissolved in carbondisulfide.

[Not all of the previously proposed procedures for this'reaction havebeen entirely satisfactory. In the earlier stages of the art, productionwas carried out in batch operation. In U. S. Patent 1,911,716 acontinuous process is disclosed. Other continuous processes since havebeen proposed. In none of these proposals has there been anysatisfactory method whereby the carbon disulfide can be separated andrecovered from the reaction mixture or the reaction products. Because ofits intrinsic value and because it is used in excess and in appreciablylarge quantities, the demand remains for a process whereby it can beseparated and recovered.

It is, therefore, a principal object of the present invention to developa continuous process for the production of mercaptoarylthiazoles whereinany carbon disulfide mixed with the reaction product gases may be.economically separated and recovered. Further objects of the inventionare to provide a novel, continuous process for the production ofZ-mercaptobenzothiazole from aniline, sulfur and carbon disulfide withprovision for the separation of carbon disulfide from the resultanthydrogen sulfide.

These objects have been met by a procedure in and vapor mixture from theseparator under conditions of temperature and pressure such that themixture when throttled down to pressures slightly above atmospheric iscooled sufliciently so that substantially all the carbon disulfide isliquefied.

Operation of the process of the present invention may bemore readilyunderstood with reference to the accompanying drawings, in which apreferred embodiment of our invention is illustrated. In the latter,Figure 1 shows, in diagrammatic form, the vertical cross sections of areactor and separator set up in a manner suitable for the conduct of theprocess of the present invention, and Figure 2 shows an additionaluseful modification of the bottom of the reactor. The process as used,is believed to be quite novel.

With reference to the drawing, it will be seen that a reactor 1comprises a vertical elongated chamber. troduce flows of the reactantsfrom any suitable sources. Conduits 2 and 3 are joined through a Tconnection to conduit 4 which enters through the top of reactor I andextends vertically down ward therethrough, almost to the bottom thereof.A curved deflector plate 5 is located near the bottom of reactor I,immediately below and at right angles to the lower or discharge end Dlconduit 4. 'A steam coil 6 is located within chamher I and aroundconduit 4. Coil 6 extends from a level near the bottom of chamber l to aheight approximately that of the normal fluid level in that chamber. Thecoil is usedto insure fluidity of the chambers content. A dischargeconduit 3 extends from an upper level in chamber I upwardly through thetop of reactor l through a pressure-controlled valve 8 and downwardlythrough the top of and into a separator vessel 9. Flow in conduit 1 isgoverned by the pressurecontrolled valve 8.

Separator 9 is also shown as, and usually will comprise, an elongatedvertical chamber. As shown, separator 9 is provided with an annuiarinner sleeve I0 extending from a level slightly which preheatedreactants are fed to a high pressure reactor; the reaction is carriedout therein in the liquid phase at elevated temperatures and pressure;the liquid and gaseous reaction products are throttled down in pressureand transferred to a separator and the separator is operated so as abovethe lower or discharge end of conduit downwardly to a level near thebottom of the separator. Outside sleeve I0 is provided a liquiddischarge conduit H extending from a level considerably below thedischarge end of conduit 7 upwardly through'the top of separator 53 andto any suitable receiver. The latter is not shown as it is conventionalin form. A gas discharge conduit [2 extends upwardly from the top ofseparator 9, through a pressure controlled expansion valve 13 and toanother suitable receiver which again being conventional is not shown.

Separator 9 is provided with suitable flanges Conduits 2 and 3 areprovided to in-- its height with a steam coil 20 surrounding sleeve In.

In Figure 2, a modification of the reactor structure is shown. Thereactor answer I arid inlet conduit 4 are the same as in Figure. 1..However, a short annular sleeve 2| is provided around the lowerpend ofconduit l Sleeve. 2| extends a short distancekaboye andbelow the end ofconduit 4. Below sleevell a mechanical agitator blade 22 is provided,being mounted on the end of and supported byashaft li which enterschamber I through, a suitable packing gland; 24. The function ofvthisarrangement is to produce a localized circulation and agitationoffiuid near the bottom of chamber l and thus, insure p o t and efficientinitiation oi the reaction.

Taking the typical reaction of anilinewith sulfur in carbon disulfideasrillustrativa the process of the present invention inthedescribedapp-aratus is readily demonstrated. It should be borne in mindthat the principal feature oi the present invention is the separationand .rfleovery o f carbon disulfide from the by prod fif as In thillustrative case, these will be substantially Wholly hydrogen sulfide.v

If the gas mixture leaving the separal b i cooled to 20=40 G. atasuitable high pressure and it is throttled through an expansion va e toabout -15 lbs. per sq. in; pressure, the m ufre can be cooled to aboutminus40 q Atthistemperature substantially all the a carbon disulfid isliquefied. Hydrogen sulfide being morevolatile is thus readily separatedand may be kfi m the recovery system containing only small fractionofabout 3% orless of the recoverable carbon disulfide. The separation.pressure should be about 300-400 lbs per sq. in abov'e atmospheric.Belowabput00lbs per sq. in th'ei e. 'is not sufiicient coolingdeveloped; above about 4.00 lbs. per sq. in-., both harbor-1 disu-lfldeand hydrogen sulfide begin to dissolve in excess the moltenmercaptobenzothiazole. n

A principal feature of the present inv therefore, the continual andcompletesepa tion of the mercaptobenzothiazole from the carbon disulfideand byproduct gas under medians at which mercaptobenzothia zb l iHalter! w it 3 50 lbs. per sq. in. in order that the carbon disu ilde ofthe carbon disulfid" hydrogen sulfide miiitiire may be liquefied. 7

but the average separationfpressure is ab With these facts inmind, thespar-asst oi the process of this invention-may betypifled i thefollowing way. Aniline under pressure and from a suitable source, willbe brought through conduit 2 and sulfur in carbon disulildewillwaitresses,

to the apparatus through conduit 3 These liquids will have beenpreheated to about 240 :C. and be under pressure of about 1 200 lbs. persq. in. varied somewhat. A minimum pmheattemperature is about 220 C. maybe increased to as These temperatures and pressures may be -reactantsareto stay properly dissolved. There 'is iio irgmrediate upperv limit onthe; pressure.

However, above about 1500 lbs. per sq. in. the cost for necessarypressure equipment becomes cessi liquids; preheated and under pressure,

are combined and forced by the pressure through conduit} to the; bottomof the reactor, being dis- 4. vThe efiect o tribute the flow over thebottom of the reactor charged through th open lower end of conduit icurved reflector plate 5 is to disandstarttne u ward rise at a uniformlydistribute'd rate; if the arrangement of Figure 2 is rs le e (h dro en'mo sph'erfc pressure to a sass n id mixtiire u a11y.jbut riot neces- J-is of course, liylousthat the used;-, the agitation and recirculationat the bottom of the autoclave ouickly initiates reaction and again theupward now is uniformly distributed.

. ffh'e faste s" uiider raises; the insome; re tant'sm es t army throughthe reader. Evolution of hy'dr s n sulfide gas eo tinues throughout thereaction sna rovms sufficient agitation of the liquids. A normal liquidlevel de'velops atabdutthe level of. the intake. to discharge conduit 1,a gas ust er; forming above this. When the pressure becomes sufficientlyhigh, emanate eis hsre er gas and I liquid through conduit 11st 'ittedby thie'. pressuree v I V ttr issettqcischarge i presses of 300-400 lbs.per sq. in., usu 1y about-i350. lesser s Gasand/m1 liquid'difscharge byvalve 8 enters separato' 9, being discharged from conduit 1 into the nsdz jff in a esmtb' 'e e mal liquid level. "The discharged material passesra idly.d weth wgh ee e '9 m bo of the separator 'an'djtacg upthrouglithe 'anu a f de b ween e s eve r' dt ersnen. Frees: g is.prevent'edby the steam coil 20. E eparati not gasa d liquid isompltedthreih, the hydrogeri; sulfide an'd remaining 'carbo'n'disulil'deiorming an upper gas cushion.

MA wears above, the separatonis mounted apparatusfsuch as a plat- '1turn. through pressure- 9 e enll aedypre -lea in l ai. d sc-h fl L ltenrr iit b s d rece nm se sm f equip nti-n w oductissoli'difledwith I itis re ted to iorm a salt sfich. as sodium 'mreaptobsnza h azele-u.

he a SUIT i lh d wn-impis lied eitpan' on valve T3 to about aAtthelopver ressurejas su -st fitially all th e ass-apt stabs am ga ar erenal and are disulfl de recovered.

is s a l 9 sure at elevated temperature;

efiectuatethe various stages of the process. Obviously, any pressurevessel of any desirable shape which is built strongly enough to confinethe reaction materials at the desired reaction pressure and temperaturewill be completely suitable for the reaction vessel. Circulating systemsfor the reactants and products may be either of a mechanical nature ortake advantage of the various physical phenomena such as convention. Ifdesired, speecial types of contacting surfaces and heat exchangers maybe introduced into both the reactor and the separator for whatever aidthey may lend to achieving reaction equilibrium. The control valvesbetween the reactor and separator and between the separator andreceivers may be of any of the various pressure sensitive devicespresently on the market. The weighing device for the separator, it isobvious, will operate effectively by pure mechanical linkage to thecontrol valves. However, it is obvious that other linkages may be usedranging from manual control to electronic devices.

Theprccess is not necessarily limited to the particular reaction ofaniline, sulfur and carbon disulfide. It is equally applicable to otherpressurized reactions wherein two gases, one of which is considerablymore easily liquefied than the other, must be separated. A number ofsimilar reactions involving hydrogen sulfide and carbon disulfide arenoted in U. S. Patent No.

It will be apparent also that the temperatures and pressuresspecifically discussed for the illustrative example may be varied withinpractical limits to meet the desired operation of the process. They maybe varied not only in accordance with the desire to change conditionsfor this reaction but also in accordance with conditions controlled bythe use of other reactants in other reactions. The process is thereforeof general application in the production of mercaptoarylthiazoles aswell as to mercaptobenzothiazoles.

We claim:

1. In a continuous process of producing mercaptoarylthiazoles whereinliquid reactants including CS2 are introduced into one end of a reactingmass held under high reaction presreacted liquid mass containing CS2 isdischarged together with by-product HRS from the opposite end; thedischarge is introduced into the lower levels of a volume of moltenreacted mass held under lower separating pressure; CS: vapor and H28 isseparated therefrom and accumulated above the separating mass; gasmixture is discharged from the accumulation; and CS: and 1128 freeproduct is discharged from the separating mass: the procedure forrecovering CS2 which comprises maintaining the reaction temperatureabove the melting point of the product mercaptoarylthiazole at thereaction pressure and the pressure above about 1000 lbs/sq. in. andsufficiently high to keep the reactants dissolved; maintaining theseparating mass at a temperature at which substantially all the CS2 isvaporized, the mercaptoarylthiazole is molten. and substantially all theCS2 and H28 is insoluble therein; maintaining the separation pressure atabout 300-400 lbs/sq. in. and such that throttling the discharge vapormixture down to about 5-15 lbs. per. sq. in. will liquefy substantiallyall the carbon disulfide; discharging and throttling the separatedgas-vapor mixture down to about 5-15 lbs. per. sq. in. and separatingthe liquid carbon disulfides from the residual discharged gases andvapors.

2. A process according to claim 1 in which a substantially constant massof separating mixture is maintained by measuring the total weight of theliquid mass and the weight of the accumulated gas separated therefrom;and discharging sufficient liquid and gaseous reaction products tomaintain this weight substantially constant.

3. In a continuous process of producing 2- mercaptobenzothiazole whereinliquid reactants including CS2 are introduced into one end of a reactingmass held under high reaction pressure at elevated temperature; reactedliquid mass containing CS2 is discharged together with by-product HzSfrom the opposite end; the discharge is introduced into the lower levelsof a volume of molten reacted mass held under lower separating pressure;CS2 vapor and H25 is separated therefrom and accumulated above theseparating mass; gas mixture is discharged from the accumulation; andCS2 and H28 free product is discharged from the separating mass: whichcomprises maintaining the reaction temperature at about 220 300 C. andthe reaction pressure at about 1000-1500 lbs/sq. in. maintaining theseparating mass at a temperature at which the 2-mercaptobenzothiazole ismolten and a pressure of 300-400 lbs/sq. in.; discharging and throttlingthe separated gas-vapor mixture down to about 5-15 lbs/sq. in. andseparating the resultant liquid carbon disulfide from the residualdischarged gases and vapors.

HAL B. H. COOPER. CARL E. MENSING.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1 1,911,716 Saunders May 30, 19332,247,894 Smith July 1, 19%1

1. IN A CONTINUOUS PROCESS OF PRODUCING MERCAPTOARYLTHIAZOLES WHEREINLIQUID REACTANTS INCLUDING CS2 ARE INTRODUCED INTO ONE END OF A REACTINGMASS HELD UNDER HIGH REACTION PRESSURE AT ELEVATED TEMPERATURE; REACTEDLIQUID MASS CONTAINING CS2 IS DISCHARGED TOGETHER WITH BY-PRODUCT H2SFROM THE OPPOSITE END; THE DISCHARGE IS INTRODUCED INTO THE LOWER LEVELSOF A VOLUME OF MOLTEN REACTED MASS HELD UNDER LOWER SEPARATING PRESSURE;CS2 VAPOR AND H2S IS SEPARATED THEREFROM AND ACCUMINATED ABOVE THESEPARATING MASS; GAS MIXTURE IS DISCHARGED FROM THE ACCUMULATION; ANDCS2 AND H2S FREE PRODUCT IS DISCHARGED FROM THE SEPARATING MASS; THEPROCEDURE FOR RECOVERING CS2 WHICH COMPRISES MAINTAINING THE REACTIONTEMPERATURE ABOVE THE MELTING POINT OF THE PRODUCT MERCAPTOARYLTHIAZOLEAT THE REACTION PRESSURE AND THE PRESSURE ABOVE ABOUT 1000 LBS./SQ. IN.AND SUFFICIENTLY HIGH TO KEEP THE REACTANTS DISSOLVED;